Identification genus Metopograpsus (brachyura:Grapsidae) based on molecular and ultrastructure studies

Worldwide, the genus Metopograpsus consists of six species . Metopograpsus thukuhar and Metopograpsus messor are common species belong to the genus that found in the Persian Gulf.. These two species are morphologically very similar to each other; as a result, their recognizing is morphologically very confusing. The existence of cryptic and sibiling species are common in marine crustaceans. The aim of this study was to evaluate whether the six morophotypes (A-E) from Metopograpsus are genetically differentiated or not, and thus, it used molecular data (mitochondrial COI) with emphasis on ultrastructure of the male first gonopod to explore evolutionary relationships in this genus. The results of present study showed that the nucleotide sequence of the mitochondrial gene fragment (COI) is not identical in all samples examined and from these 6 morphotypes ,Metopograpsus sp.PGE species was more different with other morphotypes and it was placed in a separate clade. Ultrastructure Study of the apical part of the first male gonopods showed that there are differences in the apical part of 6 color morphtypes. what was obtained from this study showed that It is very important to investigate the first male gonopod based on the COI gene in separation of species since, identification of species is difficult for many similarities morphology.